# Stack
class Stack(object):
    def __init__(self):
        self.items = []

    def push(self,item):
        return self.items.append(item)

    def pop(self):
        return self.items.pop()

    def peek(self):
        return self.items[len(self.items)-1]

    def is_empty(self):
        return self.items == []

    def size(self):
        return len(self.items)

x,y = 5,6
print(f'{x},{y}')